112 Dr. Henri/ on Urinary Calculi. [Feb. 



Urate of ammonia, I believe with Mr. Brande, has been erro- 

 neously set down by Fourcroy and Vauquelin as an ingredient of 

 urinary calculi. At least I have never found any indications of 

 its presence in calculi which had been previously subjecte'd to 

 the successive action of alcohol and of acetic acid ; menstruaj 

 which would remove urea and the ammoniaco-magnesian phos- 

 phate, but would not, in the quantities employed, have separated 

 urate of ammonia. 



Several opportunities have been thrown in ray way of examin- 

 ing urinary calculi, extracted from persons wlio had been long- 

 under a course of caustic alkaline lixivia. In one of these 

 (No. 13 of Mr. Ingham's collection) the outer surface of trfe 

 calculus might, on first view, have been supposed to have been 

 eroded ; but a closer examination satisfied me that the appear- 

 ance was owing, not to the solution of the uric acid, of which 

 the concretion chiefly consists, but to an irregular deposit of the 

 earthy phosphates, occasioned probably by the medicine. Ano- 

 ther calculus in the same collection (No. 15) taken from a 

 person who had long been using Perry's solv^ent, was so brittle, 

 that on attempting to divide it by the saw, it separated into con- 

 centric coats, composed of luic acid with a large proportion of 

 the earthy phosphates. The third is a fusible calculus, now in 

 my possession, of remarkable whiteness and compactness, and 

 containing no appreciable portion of uric acid. In a fourth 

 instance, a calculus, put into my hands by Dr. Brown, of Glas- 

 gow, which had been taken from a person after so free an use of 

 alkaline medicines as to have injured his general health, con- 

 sisted chiefly of the triple phosphate of ammonia and magnesia. 

 It was so brittle that it broke almost into powder under the 

 forceps, and was, therefore, extracted by the scoop. These 

 cases,' and others of the same kind, which 1 think it unnecessary 

 to mention, tend to discourage all attempts to dissolve a stone 

 supposed to consist of uric acid, after it has attained consider- 

 able size in the bladder ;, all that can be effected under such 

 circumstances by alkaline medicines appears, as Mr. Brande has 

 remarked,* to be the precipitating upon it a coating of the 

 earthy phosphates from the urine, a sort of concretion which, as 

 has been observed by various practical writers, increases much 

 more rapidly than that consisting of uric acid only. The same « 

 unfavourable inference may be drawn also from the dissections 

 of those persons in whom a stone has been supposed to,be dis- 

 solved by alkaline medicines ; for in these instances it has been 

 found either encysted or placed out of the reach of the sound by 

 an enlargement of the prostrate gland. The former source; of 

 fallacy was shown to have existed even in one of the cases which 

 procured to Mrs. Stevens the parhamentary reward of 5000/. j't 



* Philosoplucal Transactions, 1808. 



f Newman's Inquiry into the Merits of Solvents, LondoO) 1181. 



